3. why doesn't the temperature of the water change while the ice is melting or boiling?
(what is happening to the heat energy? )

In other words, the water molecules within ice move faster. However, temperature doesn't change as heat is added during a phase change; for example, when the ice melts. During the phase change, the added heat doesn't make the molecules move faster, but rather further apart.

Explanation:

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.